Scientific Forecaster Discussion

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
1250 PM EDT SUN APR 20 2014

.UPDATE...
AVIATION SECTION HAS BEEN UPDATED BELOW.

&&

.SYNOPSIS...
ISSUED AT 345 AM EDT SUN APR 20 2014

HIGH PRESSURE WILL MAINTAIN PLEASANT WEATHER ACROSS THE OHIO VALLEY 
INTO MONDAY. A COLD FRONT WILL MOVE THROUGH THE OHIO VALLEY MONDAY 
NIGHT WITH SHOWERS AND ISOLATED THUNDERSTORMS. DRY AND COOLER 
WEATHER IS EXPECTED FOR MIDWEEK...WITH A RETURN TO WARMER AND MORE 
UNSETTLED CONDITIONS THURSDAY AND FRIDAY AS ANOTHER COLD FRONT 
TRACKS INTO THE OHIO VALLEY. COOLER AND DRIER WEATHER RETURNS AGAIN 
FOR NEXT WEEKEND.

&&

.NEAR TERM /REST OF TODAY/...
ISSUED AT 1019 AM EDT SUN APR 20 2014

TODAY/S HIGHS MAY BE A FEW DEGREES ON THE WARM SIDE BASED ON THIS 
MORNING/S UPPER AIR...BUT CURRENT TEMPERATURES RUNNING CLOSE TO WHAT 
WAS EXPECTED BY THIS TIME...SO WILL LEAVE THE HIGHS ALONE FOR NOW.

NO UPDATES PLANNED AT THIS TIME. PREVIOUS DISCUSSION FOLLOWS.

SURFACE HIGH PRESSURE RIDGE RESIDES ACROSS THE OHIO VALLEY EARLY 
THIS MORNING WITH MAINLY CLEAR SKIES ACROSS THE REGION. WIDE 
RANGE OF TEMPS AS OF 07Z...RANGING FROM THE UPPER 30S TO THE LOWER 
50S.

THE SURFACE RIDGE WILL REMAIN FIRMLY ENTRENCHED ACROSS THE OHIO AND 
TENNESSEE VALLEYS TODAY WITH BLOCKING LOW PRESSURE OFF THE SOUTHEAST 
COAST. OTHER THAN PERIODS OF CIRRUS THROUGHOUT THE DAY...EXPECT 
ABUNDANT SUNSHINE WITH MODEL SOUNDINGS INDICATING CONTINUED DRY AIR 
AND SUBSIDENCE BELOW 15-20KFT. SURFACE FLOW WILL GRADUALLY VEER TO 
S/SE DURING THE AFTERNOON AS THE RIDGE AXIS SHIFTS EAST INTO THE MID 
ATLANTIC AND APPALACHIANS. 

TEMPS...ANOTHER OUTSTANDING DAY WITH AFTERNOON HIGHS RISING WELL 
INTO THE 70S AS 850MB TEMPS CLIMB TO AROUND 10C. FOLLOWED 
PERSISTENCE YET AGAIN...GOING ABOVE MOS BY A DEGREE OR TWO FOR HIGH 
TEMPS. 

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
ISSUED AT 345 AM EDT SUN APR 20 2014

FORECAST CHALLENGES FOCUS ON PRECIP CHANCES WITH A COLD FRONT MONDAY 
AFTERNOON AND NIGHT.

LOW PRESSURE WILL FINALLY BEGIN TO PULL AWAY FROM THE CAROLINA COAST 
TONIGHT AND MOVE FURTHER OUT INTO THE ATLANTIC OCEAN ON MONDAY. 
RIDGING ALOFT AND THE SURFACE WILL SHIFT TO THE EAST COAST BY 
MONDAY...ENABLING A WAVE ALOFT MOVING THROUGH THE CENTRAL PLAINS 
TONIGHT WITH AN ASSOCIATED COLD FRONT TO TRACK INTO THE OHIO VALLEY 
BY LATE MONDAY. THE UPPER WAVE WILL BECOME ABSORBED BY A STRONGER 
WAVE MOVING ACROSS THE NORTHERN GREAT LAKES WITH LOW PRESSURE 
DEEPENING AS IT TRACKS INTO UPSTATE NEW YORK ON TUESDAY MORNING. 
WEAK LOW LEVEL CONVERGENCE ALONG THE BOUNDARY IN TANDEM WITH A 
PERIOD OF ISENTROPIC LIFT MONDAY NIGHT WILL BE THE PRIMARY 
CATALYSTS FOR SHOWERS. INSTABILITY REMAINS WEAK AT BEST WITH ANY 
THUNDER ANTICIPATED TO BE ISOLATED AND EMBEDDED WITHIN THE RAIN. 

INITIALLY...DRIER AIR THROUGH THE BOUNDARY LAYER WILL BE SLOW 
TO ERODE...WITH PRECIP CHANCES NOT ARRIVING UNTIL LATE AFTERNOON 
MONDAY AND BECOMING MORE WIDESPREAD MONDAY EVENING. WILL MAINTAIN 
LIKELY POPS MONDAY NIGHT WITH RAINFALL ENDING BY 12Z TUESDAY AS THE 
FRONT QUICKLY MOVES EAST. HIGH PRESSURE WILL REESTABLISH DURING THE 
DAY TUESDAY AS MUCH DEEPER SUBSIDENCE EXPANDS BACK INTO THE REGION 
FROM THE NORTHWEST. PRESENCE OF COLD ADVECTION AND A WEAK WAVE ALOFT 
TRAILING THE BOUNDARY WOULD ARGUE FOR CU DEVELOPMENT DURING THE 
COURSE OF THE DAY...BUT THE AMOUNT OF DRY AIR ADVECTING IN MAY KEEP 
CLOUD COVERAGE LIMITED TO SOME DEGREE. REGARDLESS OF THE AMOUNT OF 
CLOUDS ON TUESDAY...SKIES WILL CLEAR TUESDAY NIGHT AS THE HIGH 
CENTERS OVER THE REGION. 

TEMPS...WITH MOST OF THE RAIN LIKELY TO HOLD OFF UNTIL LATE DAY AT 
THE EARLIEST...ONCE AGAIN GOING AT OR JUST ABOVE WARMER METMOS 
GUIDANCE FOR HIGHS MONDAY. LOW LEVEL THERMALS SUPPORT HIGHS INTO THE 
MID/UPPER 60S. ENDED UP TAKING A SPLIT OF THE COOLER MAV AND WARMER 
MET. PRESENCE OF DRY AIR THROUGH THE BOUNDARY LAYER TONIGHT WILL 
SUPPORT A DECENT RANGE IN LOWS FROM THE UPPER 40S TO MID 50S BETWEEN 
THE RURAL LOCALES AND THE CITIES. NEAR MOS GUIDANCE ON MONDAY NIGHT 
WITH RAIN AND CLOUDS...THEN UNDERCUT MOS TUESDAY NIGHT WITH COLD 
ADVECTION AND NORTHERLY FLOW. DEPENDING ON HOW QUICKLY THE LOWER 
LEVELS DECOUPLE...SOME FROST ACCRUAL POSSIBLE WITH LOWS FALLING INTO 
THE MID/UPPER 30S. 

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
ISSUED AT 307 AM EDT SUN APR 20 2014

FAIRLY TYPICAL SPRINGTIME WEATHER EXPECTED ACROSS CENTRAL INDIANA 
FOR THE LONG TERM PORTION OF THE FORECAST. MODELS INDICATE ONE 
SYSTEM TO MOVE FAIRLY QUICKLY THROUGH THE AREA THURSDAY INTO FRIDAY. 
PROGRESSIVE NATURE OF THE SYSTEM SUGGESTS POPS SHOULD BE CONFINED TO 
THURSDAY AFTERNOON AND PERHAPS LINGER AS LONG AS FRIDAY 
MORNING...BUT WILL CARRY THEM NO FURTHER. TOWARD THE VERY END OF THE 
PERIOD A WARM FRONT IS DEPICTED APPROACHING THE AREA AND WILL CARRY 
CHANCE POPS FOR THAT.

MODEL PROGS FOR BULK SHEAR...K INDEX AND CONVECTIVE PRECIP INDICATE 
ORGANIZED CONVECTION IS A DISTINCT POSSIBILITY THURSDAY AFTERNOON 
AND EVENING...BUT THERE REMAINS TOO MUCH MODEL AND RUN TO RUN 
DISCREPANCY TO SUGGEST AN ORGANIZED SEVERE THREAT.

MAX TEMPS NEEDED BUMPED UP ACROSS THE BOARD AS MODEL 850 MB TEMPS 
AND LOW LEVEL THICKNESSES SUGGESTED THEY WERE A BIT LOW. OTHERWISE 
ALLBLEND WAS FINE.

&&

.AVIATION /DISCUSSION FOR THE 20/18Z TAF ISSUANCE/...
ISSUED AT 1250 PM EDT SUN APR 20 2014

VFR THROUGH THE PERIOD AS A RIDGE OF HIGH PRESSURE ACROSS OUR AREA 
MOVES TO THE EAST. 

ONLY SCATTERED HIGH CLOUDS THIS AFTERNOON AND EARLY TONIGHT WITH 
SOME MID CLOUDS AND BROKEN HIGH CLOUDS LATE TONIGHT.  ON MONDAY 
THERE MAY BE SCATTERED CU BY LATE MORNING WITH INCREASING MID/HIGH 
CLOUDS DURING THE DAY. AN ISOLATED THUNDERSHOWER IS POSSIBLE LATE 
MONDAY...BUT CHANCES ARE TOO LOW TO INCLUDE AT THE END OF KIND 30 
HOUR TAF AT THIS TIME.

LIGHT SOUTH WINDS OF 7 KNOTS OR LESS WILL BECOME SOUTHWEST UP TO 12 
KNOTS MONDAY AS A COLD FRONT APPROACHES FROM THE NORTHWEST. 

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE. 

&&

$$

SYNOPSIS...RYAN
NEAR TERM...RYAN/JAS
SHORT TERM...RYAN
LONG TERM...NIELD
AVIATION...JH

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